The present invention relates to microcapsules and a process for producing them. More particularly, the present invention relates to microcapsules and a process for producing, by wax coating or coating with a mixture of wax and protein, microcapsules which are preferably used in feeds, [particularly, feeds for fries,] medicines, foods, chemical products, etc.
As described in "Technique for Surface Modification of Fine powder by Encapsulation", pages 547 to 551 (particularly page 548) of Chemical Engineering, Vol 46, No. 10 (1982), it is conventionally known that there are 14 processes for producing microcapsules, such as the interfacial polymerization process, the in-liquid drying process and the like.
The microcapsules produced according to these processes are being used in many industrial fields to prepare foods, medicines, agricultural chemicals, feeds, spices, enzymes, active carbon and the like, as described in the above literature. Of the above 14 processes, there are known, as typical processes for coating particles of a core substance with a wax, a suspension-in-gas process (a coating-in-fluid-layer process) and a melting-dispersion-cooling process (a pelletization process by spraying and solidification).
However, the above mentioned processes have defects in that degradation of the core substance particles tends to occur, that the film formed on the particles becomes scaly and no uniform film is formed, and that a large amount of a wax is required to obtain a complete film on the particles.
U.S. Pat. No. 4,675,236 discloses mono-core type microcapsules and a process for producing them.
The patent relates to wax-coated microcapsules in which the wax coating is prepared by once melting the wax particles over the surface of the core particles and then resolidifying them.
On the other hand, at present, microcapsules and a process for producing them by simultaneously coating hydrophobic waxes (in particular, lipids) and hydrophilic proteins are not known in the field.
An object of the present invention is to provide microcapsules and a process for producing them to solve the above mentioned defects associated with the conventional processes.
Another object of the present invention is to provide microcapsules and a process for producing them on which waxes or a mixture of waxes and proteins are coated uniformly.